Defrosting refrigeration system



March 5, 1957 L. A. STAEBLER E T AL DEFROSTING REFRIGERATION SYSTEM Filed Nov. 2, 1953 2 Sheets-Sheet 1 March 5, 1957 l.. A. srAEBLl-:R ErAL 2,783,621

DEFROSTING REFRIGER-ATION SYSTEM Filed Nov'. 2, 1953 2 sheets-sheet 2 z//za f www? GIA/ff DEFROSTING REFRIGERATION SYSTEM Lloyd A. Staebler, reland, and Elmer W. Zearfoss, Jr.,

Philadelphia, Pa., assignors to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application November 2, 1953, Serial No. 389,794

13 Claims. (Cl. 62-117.55)

The present invention relates to refrigerating apparatus and, briey stated, pertains to refrigerated circulating systems in which provision is made for selective operation of an evaporator either to eiect cooling of its surfaces so as to produce refrigeration, or to effect heating of its surfaces so as to melt frost accumulated thereon.

ln a general sense, the invention herein disclosed and claimed concerns defrostable refrigeration systems wherein, during a defrost cycle, hot gaseous refrigerant owing from the compressor by-passes the condenser and the restrictor and passes directly into the evaporator where it condenses and, in Ithe process, develops sufiicient heat to melt accumulated frost. in a more limited sense, the herein described and claimed invention has to do with improved ysystems in which, after initiation of a defrost cycle, liquid refrigerant ows from the evaporator into the suction line and compressor housing and evaporates therein, whereby the pressure within the system ismaintained at the required value to prevent trapping and reevaporation of condensed refrigerant within the evaporator. An improved system of this latter kind is disclosed in Zearfoss Patent No. 2,627,730, dated February l0, l953. While a system as set forth in said patent performs satisfactorily, a substantial period of time is required for liquid refrigerant to flow out ofthe evaporator so that an unnecessarily long delay occurs between the time when the defrost cycle is initiated and the time when defrosting begins to take eect due to condensation of gaseous refrigerant in said evaporator.

lt is therefore an object of this invention to provide a novel system constructed in such a manner that liquid refrigerant present in the evaporator during the normal refrigerating cycle rapidly leaves said evaporator upon inception of a defrost cycle so that there is no appreciable lag in the transition from the refrigerating to rthe defrosting functions of the system.

Another and more specific object of the invention resides in the provision of simple means which, substantially simultaneously with initiation of a defrost cycle, creates a condition expediting the fiow of liquid refrigerant out of the evaporator, and continues that condition so long as the defrost cycle is in progress.

The invention is also featured by the fact that, although automatic defrosting is provided, the charge of refrigerant within the system need not exceed that required for normal refrigeration.

In achievement of the above-mentioned general objectives, the invention employs certain features of the novel arrangement disclosed and claimed in the co-pending application of Elmer W. Zearfoss, Jr., Serial No. 385,017, filed October 8, 1953, now Patent No. 2,709,342.

The system, according to the present invention, includes a novel organization of elements whereby hot gaseous refrigerant passing directly from the compressor into rthe evaporator is utilized to effect removalof liquid refrigerant from the evaporator yat the beginning-'of 1a defrost cycle and to insure continuance of liquid removal as 2,783,63Zi Patented Mar. 5, 1957 'ice gaseous refrigerant condenses in the `evaporator throughout the defrost cycle. In particular accordance with the invention, a header which is disposed at the outlet side of the evaporator and which traps liquid refrigerant circulating through the evaporator during normal refrigeration, is supplied with a percolator element; and a bypass conduit or connection serving to deliver hot gaseous refrigerant tc vthe evaporator, is associated with said element to produce therein a percolating effect which, from the start to the termina-tion of a defrost cycle, so affects the hydrostatic balance of the system that liquid refrigerant begins, and continues, to ow out of said evaporator and header.

In accordance with a preferred embodiment of the invention, the `by-pa-ss conduit is arranged to pass hot gaseous refrigerant in heat exchange relation with the percolator element so Ithat heat which is thereby ltransferred to said element brings about a percolating action in the latter. According to a modified embodiment, the by-pass conduit is associated with 1the percolator element to deliver hot gaseous refrigerant thereinto in quantity sufficient to cause the percolating Iaction.

A feature o f the invention as embodied in either the preferred or the modified form is that -no special and intricate control means is required to modify the normal flow of refrigerant within the system and to establish the aforesaid iiow of hot gaseous refrigerant. Such modification of flow is readily and effectively obtained with the use of a simple and inexpensive device, for example an ordinary solenoid-actuated valve interposed in the hypass conduit.

Other characteristic features and the manner in which the labove-recited objectives and advantages of the invention 'are best achieved will clearly appear from the following description of the embodiments illustrated in the accompanying drawings, in which:

Figure l is a diagrammatic view of ka refrigeration system constructed in accordance with Ia preferred form of the invention; and

Figure 2 is a view similar Ito Figure l and represents a refrigeration system constructed in accordance with a modified form of the invention.

With more particular reference to the drawings, it will ybe seen that in the two forms illustrated therein, the invention employs the customary elements of a conventional refrigeration system, which elements are a compressor 1li, a condenser 11, a restrictor or capillary tube 12 and 'an evaporator 13, the latter being disposed in heat exchange relation with 1a compartment Ior zone to 'be cooled, which compartment is diagramrn-atically illustrated by broken lines identified at 14. The yaforesaid elements are connected in series flow circuit by means of suitable conduits and connections which include a conduit 15, Ia header or Aliquid trap 16 and a suction line 17.

The conduit 15 is connected with the inlet end 13 of the evaporator and with the outlet end 19 of the restrictor or capillary tube, the other or inlet end Ztl of which communicates in the usual manner with the outlet end 21 of the condenser. lf desired, a dryer 22 may be interposed at the connection between said conduit 15 and said outlet end 19 of the capillary tube.

The header or liquid trap 16 conveniently takes the -form of an elongated tank or cylinder 23 disposed with its longitudinal axis in a generally horizontal position. One end portion 24 of the header or trap 16 communicates with the outlet end 2S of the evaporator, and the other end portion 26 of said header or trap communicates with the inlet end 27 of the suction line 17 which, in the customary manner, is advantageously arranged in heat exchange relation with a portion of `the capillary tube, asis represented at` 28.

In especial accordance with the invention, the header or trap 16 is provided with means which allows it kto function, at times, as a percolator. For that purpose, said header or trap is supplied with an internal upwardly projected wall `or partition 29 and with an external downwardly projected generally U-shaped tube 30.

As shown in the drawings, the wall 29 is dispose-d within the header to divide the interior thereof into a larger chamber 31 and a smaller chamber 32, the evaporator 4discharging into said largerchamber and the suction line leading from said smaller chamber.- As also shown in the drawings, the upper edge of said wall 29 terminates at a slight distance from the upper inner surface of the header to provide a passage 33 between said chambers.

In the illustrated forms of the invention, one 'leg 34 of the U-shaped tube extends laterally for connection with a lower portion of the header 16 and for communication with said larger chamber 31 at a point adjacent the conneetion of said header with the outlet of the evaporator. The other leg 35 of said tube extends upwardly and enters said header to communicate with said smaller charnber 32, said other leg being projected to terminate at a point adjacent the upper inner surface of said header. In practice, the system is charged wi-th a predetermined quantity of refrigerant to insure that liquid refrigerant circulating through the evaporator to cool the same, will accumulate in the larger chamber 31 of said header' 16 and remain at a level which, as indicated at 36, is below the passage 33 within said header and, as indicated at 37, is below that end of leg 35 which opens into the smaller chamber 32. In this manner, liquid which lls the U-shaped tube and rises in said leg 35, does not spill out but, due to hydrostatic forces, is maintained at a level corresponding to the liquid level in said larger chamber; Accordingly said leg 35 normally provides a static column of liquid refrigerant.

However, in accordance with the invention, there is provided control means which upon initiation of a defrosting cycle functions to cause said column to rise above said level so that liquid refrigerant spills out of leg 35 into said smaller chamber 32 and through suction line 17, for the purpose to be hereinafter set forth.

In the form illustrated in Figure l, the control means includes the hereinbefore mentioned conduit 15 which has a portion 38 arranged in heat exchange relation with the U-shaped tube at a lower portion of its upstanding leg 35 and which is connected in open communication through a coupling 39 with a by-pass conduit 40. This lay-pass conduit is connected, as shown at 41S, between fthe compressor and the condenser 11 so that hot gas# eous refrigerant passing out of the compressor may be diverted through said conduit and ow in heat' exchange relation with said leg 35 of the U-shaped tube and then 4directly into the evaporator 13.

In the form illustrated in Figure 2, the mentioned control means comprises a conduit 42 of capillary tubing. As represented at 43, one end of said conduit 42 is connected with and opens into the U-shaped tube at a lower portieri of the upstanding leg 35. The other end of said conduit 42 is connected in open communication with a coupling 44 which connects the conduit- 15V with the restrictor 12. The coupling 44 is conveniently constructed to provide an elongated portion 45 adapted to retain liquid refrigerant during normal or refrigerating operation. The conduit leads from aV point along the length of said portion, and the conduit 42 exten-ds into said portion so that, during said normal operation, the inlet endof the latter conduit is submerged in liquid refrigerant, thus assuring against passage of gaseous refrigerant into the U-shaped tubeA 30. In this latter form of the invention, the by-pass conduit 40 is connected with said coupling 44 `to discharge hot gaseous refrigerant (during defrosting) at a point ahead of the portion 4S so that part' ofthe gaseous refrigerant passing out of the compressor for -delivery to the evaporator may ow through said coni 4 duit 42 of capillary tubing and enter said leg 35 of the U- shaped tube f-or the purpose to be subsequently explained.

In both forms of the invention, a valving device is employed to control the flow of gaseous refrigerant through the by-pass conduit 40. This device is in the convenient form of a solenoid valve 46 which is actuated in response to operation of a switch 47. This switch 47 advanta geously is of the single-throw double-pole type and is ineluded in the electrical circuit which energizes the compressor. As is common practice, energiz'ation of the compressor is accomplished through the function of a temperature-sensitive switch device 48 which is responsive to the pressure of a' vaporizable iiuid contained within a feeler bulb (not shown), said bulb preferably being disposed in heat exchange relation either with the evaporator or with the compartment or zone to be cooled.

`During normal operation of the system as embodied in either of the `two forms herein described,` that is during those times when defrosting is not required, closing of the switch device 48 places the .motor of the compressor across the electrical power supply line 49, and encrgizes the compressor which delivers hot compressed gaseous refrigerant to the condenser where said refrigerant is converted to liquid state. From the condenser, liquid rcfrigerant flows through the restrictor or capillary tube 12, the dryer 22, the conduit 15 and into the evaporator 13 and header 16 in which the liquid is trapped in the manner here'inbefore stated. In the'evaporator, liquid refrigerant vaporizes and thus produces the refrigeration effect which cools the evaporator surfaces. The vaporized refrigerant which bubbles through the liquid, rises in the chamber 31 of the header 16 and escapes through the chamber 32 of said header, and thence iiows through the suction line 17 and into the compressor 1G. During this normal operation of the system, the valve 46 is closed so that there is no ilow of hot gaseous refrigerant 4through the by-pass conduit 15. It will be understood that the above-described refrigerating operation' of the system occurs cyclically under controlV of the feeler bulb associated with saidY switch device 4S.

To initiate a defrosting cycle the switch 47 is closed, thus actuating the solenoidV valve 46 to open the by-pass conduit 40. Operationl of said switch may be done either manually or automatically by utilizing any of several suitable arrangements which are known in the art. It will be noted that the switch 47 is so arranged inl the electrical circuit as to cause energization of the compressor concurrently with opening of saidy by-pass conduit in the event a defrosting cycle is initiated when the switch 48 isV open andsaid compressor is idle.

In the form of the invention illustrated in Figure l, opening: of the' bypassv conduit 40V causes hot gaseous refrigerant emerging from thecompressor to ilow through said by-pass conduit and throughl the conduit 15 into the evaporator. The heat applied to the heat exchange portion 38 between said conduit 15 and the upstanding leg 35 of the U-shaped tube 30 causes evaporation of some of the liquid refrigerant within said leg. The gaseous refrigerant thus created in the legV 35 so affects the hydrostatic pressure that said tube 30 acts as a p'ercolator or vapor-lift device and causes liquid within said leg 35 to percolate.

In the form of the inventionV illustrated in Figure 2, the hot gaseous refrigerant which, upon' opening' of the valve 46 passes, throughl the by-pass conduit et) for feeding to the evaporator, fills the portion 45 so that a part of said gaseous refrigerant flows through the restrictor conduit 42 and into the leg 35 of the U-shaped tube 30. Due to the presence of gaseous refrigerant in said leg, liquid refrigerant in the U-shaped tube 30 is caused to percolate as it does in the form iilustrated in Figure 1.

The percolating action which takes place in the leg 35 of the U-sha'p'e'd tube included in either of the twov illustrated formswof theinvention unbalance's the liquidv column normally existing in said leg, and liquid refrigerant overflows into the chamber 37 and becomes available for owng into the suction line 17. The liquid refrigerant evaporates in said line and in the compressor housing, and the gas which is thus formed is pumped by the compressor to maintain the ow of hot gaseous refrigerant through oy-pass conduit 40 and into the evaporator 13. It will be understood that as soon as the hydrostatic balance in the system is disturbed and the liquid begins to emerge from the U-shaped tube, liquid in the header and in the evaporator drains out, the drainage being the result of the combination of the continued percolating action which takes place in the U-shaped tube and the concurrent expelling action which is brought about by the on-rush of hot gaseous refrigerant into the evaporator. The hot gaseous refrigerant which replaces the liquid leaving the evaporator gives up its heat to the frost laden evaporator surfaces with the result that condensation occurs in the evaporator at the same time as defrosting is accomplished. Because the above noted drainage action is continuous, it will be apparent that the evaporator is continually ridding itself of condensate as it is formed in said evaporator. It will also be apparent that any liquid refrigerant which may flow out of the restrictor or capillary tube 12 and enter the conduit 15 at the connection 39 (Figure l) or at the connection 44 (Figure 2) will quickly evaporate in the presence of hot gaseous refrigerant and thus will not interfere with the defrosting function of the system.

With reference to Figure 1, it is pointed out that the refrigerating function of the system is not adversely affected by the fact that the conduit 15 is in heat exchange relation with the U-shaped tube 30. The reason is that during the refrigeration cycle, cold liquid refrigerant flows through said conduit and, therefore, cools rather than heats the column of liquid in the leg 35 of the U-shaped tube.

With reference to Figure 2, it is pointed out that the internal diameter of the restrictor tube 42 as compared with the internal diameter of conduit 15 is such that during a refrigeration cycle the amount of refrigerant which passes through said tube is practically nil and insufiicient to disturb the liquid column in the leg 35 of the U-shaped tube 30. Accordingly, the normal hydrostatic condition which exists during the refrigerating function remains unaffected.

It is to be understood that, in practice, the header 16 and its associated U-shaped tube 30 would be enclosed in insulation so that liquid refrigerant trapped in said header and tube is not affected by heat transfer with ambient atmosphere.

From the foregoing description, it will be appreciated that the present invention provides a simplified defrostable refrigerating system which is characterized by extraordinary rapidity with which defrosting of an evaporator can be accomplished. Particularly, it will be recognized that the arrangement which utilizes heat present in the system to effect prompt evacuation of liquid refrigerant from said evaporator at the initiation of and during a defrosting cycle is a distinctively important feature of the invention. Moreover, the arrangement which includes the header at the outlet of the evaporator and the means operable to cause liquid refrigerant to ow from said header at the beginning of and throughout a defrosting cycle, is significant in that it eliminates the necessity of cucumber-ing the system with an unnecessary surplus of refrigerant to effect defrosting.

We claim:

l. An arrangement for controlling the operation of a defrostable refrigerating system provided with an evaporator and refrigeran-t circulating means adapted, under one condition of operation, to pass liquid refrigerant to said evaporator to cool the same and, under another condition of operation, to pass gaseous refrigerant to said evaporator to heat the same; said arrangement comprising: a re- `frigerant trap connected with the outlet of said, evaporator and having a conduit portion inwhich liquid refrigerant accumulate-s in a static column which, during 4said one condition of operation, prevents the escape of liquid refrigerant from said trap through said conduit portion; and control means for initiating said other conditonjof operation and including a conduit to deliver gaseous refrigerant for passage into said'evaporator, said conduit being provided with means associated with the mentioned conduit portion of said trap to provide for the presence of evaporated refrigerant within said portion to affect said column of liquid refrigerant in such manner as 'to cause liquid refrigerant which is present in said trap and evaporator to flow therefrom and-to escape through said conduit portion. j l

2. An arrangement for selectively controlling the flow of refrigerant through an evaporator either to cool or to heat the same, comprising: a refrigerant receiving header connected with theyoutlet of the evaporator and having a portion in which liquid refrigerant accumulates after circulation through said evaporator to cool the latter; pas` sage means leading from said portion of said header at a point normally above the level of .said accumulated liquid refrigerant and providing for the escape of vrefrigerant which evaporates in circulating through said evaporator; conduit means leading from said portion of said header at a point normally below the level of said accumulated liquid refrigerant and having a portion for trapping liquid refrigerant in a static column which normally prevents the escape of liquid refrigerant through said conduit means; andcontrol means including a conduit leading to said evaporator to deliver gaseous refrigerant for circulation through said evaporator to heat the same, said conduit being provided with means associated with said liquid trapping portion of said conduit means to provide for the presence of evaporated refrigerant within said portion to affect said `column of liquid refrigerant in such a manner that liquid refrigerant which is present in said trap and evaporator flows therefrom and escapes through said conduit means.

3. An arrangement as set forth in claim 2, in which the mentioned header is internally divided to provide an inlet chamber and an outlet chamber, and in which the mentioned conduit means leads from said inlet chamber and discharges into said outlet chamber.

4. A defrostable refrigerating system comprising: a compressor, a condenser, an evaporator, `and conduits including a restrictor and a suction line connecting said compressor, condenser and evaporator in series ow circuit; refrigerant passage means interposed between said evaporator and said suction line and including an accumulator portion for receiving liquid refrigerant from said evaporator and a conduit section for receiving liquid refrigerant from said portion, said conduit section being upwardly directed for trapping said liquid refrigerant in a static column which prevents the flow of liquid refrigerant from said portion through said section, and control means including Ia bypass conduit connected to deliver gaseous refrigerant from said compressor directly into said evaporator, said by-pass conduit having means associated with said -conduit section to provide for the presence of gaseous refrigerant Within said conduit section and so yaffecting said column of liquid refrigerant as to cause liquid refrigerant to flow from said accumulator portion through `said conduit section.

5. A defrostable refrigerating system as set forth in claim 4, in which the mentioned means associated with the mentioned conduit section is provided by a portion of the mentioned by-pass conduit arranged in heat exchange relation with said conduit section.

6. A defrostable refrigerating `system as set forth in claim 4, in which the mentioned means associated with mentioned conduit section is provided by Ia flow restricting tube portion connected with the mentioned by-pass conavancer 7 duit-and opening into said conduit section to deliver the-rein ametered quantity of gaseous refrigerant.

7. Aqdefrostable refrigerating system as set forth in claim 6, in which the connection between the mentioned restricting tube portion and by-pass conduit includes a refrigerant collecting portion into which said tube portion extends.

8. A defrostable refrigerating system comprising: a compressor, a condenser, an evaporator, and conduits including a restrictor and a suction line connecting said compressor, condenser and evaporator in series ow circuit; a header divided into two chambers,` one of said chambers communicating with the outlet end portion of said evaporator and the other of said chambers communicating with the inlet end portion of said suction line, said' one of said chambers being adapted normally to trap liquid refrigerant flowing from said evaporator; means defining. av passage leading to said other of said chambers' from a point above the level of the liquid refrigerant trapped in said one of said chambers to pass evaporated refrigerant int-o said other of said chambers and through said suction line into said compressor; means defining a second passage leading to said other of said chambers from a point below the level of the liquid refrigerant trapped in said `one of said chambers and having a generally vertical section extending int-o said other of said chambers -to a point above said level' so that liquid refrigernt in said section normally rises to a level cor-A responding to the level of the liquid refrigerant in said one ofsaid chambers and is normally prevented from passing into said -other Iof said chambers; control means including a third passage leading from said compressor directly to said evaporator -to deliver gaseous refrigerant for circulation through said evaporator, said third passage being associated with said second passage to provideV for the presence of gaseous refrigerant within said vertical section and cause-liquid refrigerant to rise above said level and to now out `of said second passage thereby initiating flow of liquid -refrigerant from said evaporator through said section and into said suction line to evaporate therein; and means for controlling the operation of said control means.

9. A refrigerant circulating system selectively operable either to cool or to heat an evaporator, said system corn'-` prising: a compressor, a` condenser, an evaporator and conduits including a restrictor and a suction line connecting" said compressor, condenser and evaporator'V in series flow circuit; a header interposed between said evaporator and suction line and having 'an internal partition dividingthe interior of said header into two chamb'e'rs, said evaporator discharging into one of said charnbers and said suction line leading from the other of said chambers, said one of said chambers trapping liquid refrigerant owing from said evaporator to a predetermined normal level, said header further having two distinct passages each establishing communication between said chambers, one of said passages leading from a portion of said one of said chambers above said normal level to provide for escape of evaporated refrigerant into the other of said chambers and through said suction line into said compressor, the other of said passages leading Vfrom a portion of said one of said chambers below said level to provide for passage of liquid refrigerant into the other of said chambers, said other of said passages having a substantially verticallyextended section opening in said other of said chambers above said normal level so that liquid refrigerant stands in said section to a level corresponding to said normal level and is prevented from passing into said other of said chambers; control means including a by-pass conduit connected to deliver gaseous refrigerant from said compressor directly into said evaporator, said by-pass conduit being associated with said other of said passages to subject liquid refrigerant therein to the heat of said gaseous refrigerant and cause liquid refrigerant standing in said section to risc 'above said level and to flow out of said other of said passages thereby providing for passage of liquid refrigerant from said evaporator through said chambers and into said suction line; and means operable to initiate land terminate the operation of said control means.

l0. A refrigerant circulating system selectively operable either to cool or to heat anv evaporator, said system comprising: a compressor, a condenser, an evaporator, and conduits including a restrictorV :and a suction line connecting said compressor, condenser and evaporator in series flow circuit; a header interposed between said evaporator and suction line; a partition dividing the interior of said header into two chambers and having means providing a passage between said chambers, said evaporator discharging into one of said chambers and said suction line leading from the other of said chambers, said one of said chambers trapping liquid refrigerant flowing from said evaporator to a normal level below said passage, said passage providing for the escape of evaporated refrigerant into -said other of said chambers and through said suction line into said compressor; a generally U- shaped tube dependingfr'om said header, one leg of said tube being connected with said header to pass liquid refrigerant from said one of said chambers, the other leg of said tube entering said other of said chambers and terminating at a point above said normal level so that liquid refrigerant passing into said U-shaped tube stands therein up to a level corresponding to said normal level; control means including a conduit by-passing said condenser and restrictor to deliver gaseous refrigerant from said compres-sor directly into said evaporator, said conduit having means associated with said U-shaped tube to provide for the presence of gaseous refrigerant within said other leg of said tube and create therein a percolating effect which causes liquid refrigerant standing in said U-shaped tube to rise above said level and to spill into said other of said chambers thereby providing for passage of liquid refrigerant from said evaporator through said chambers into said suction line to evaporate therein.

ll. A refrigerant circulating system as set forth in claim l0, in which the mentioned means associated with said U-shaped tube is provided by a portion of said bypassing conduit arranged in heat exchange relation with said tube.

12. A refrigerant circulating system as set forth in claim l0, in which the mentioned means associated with said U-shaped tube is provided by a now restricting tube connected with said by-p-assing conduit and opening into said other leg of said U-shaped tube to deliver thereinto a metered quantity of gaseous refrigerant.

13. A refrigerant circulating system as set forth in claim l2, in which the connection between said restricting tube and said by-passing conduit includes a refrigerant collecting portion into which said tube extends.

References Cited in the le of this patent UNITED STATES PATENTS 2,641,908 La Porte lune 16, 1953 2,678,545 Zearfoss a May 18, 1954 2,693,683 Toothman Nov. 9, 1954 

